![Allen Pinkerton at left + group at quarters of Secret Service Army of Potomac October 1862 - Digital Commonwealth Allen Pinkerton at left + group at quarters of Secret Service Army of Potomac October 1862 - Digital Commonwealth](https://bpldcassets.blob.core.windows.net/derivatives/images/commonwealth:rv043941n/image_access_800.jpg)
Allen Pinkerton at left + group at quarters of Secret Service Army of Potomac October 1862 - Digital Commonwealth
![Alexander Gardner | [President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department, Alexander Gardner | [President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department,](https://images.metmuseum.org/CRDImages/ph/original/DP285633.jpg)
Alexander Gardner | [President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department,
![Antietam, Maryland (vicinity). Maj. Allan Pinkerton, Secret Service Department and friends - PICRYL Public Domain Search Antietam, Maryland (vicinity). Maj. Allan Pinkerton, Secret Service Department and friends - PICRYL Public Domain Search](https://cdn4.picryl.com/photo/1862/01/01/antietam-maryland-vicinity-maj-allan-pinkerton-secret-service-department-and-1-1024.jpg)
Antietam, Maryland (vicinity). Maj. Allan Pinkerton, Secret Service Department and friends - PICRYL Public Domain Search
![President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department, Headquarters Army of President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department, Headquarters Army of](https://c8.alamy.com/comp/2H6B3FM/president-abraham-lincoln-major-general-john-a-mcclernand-right-and-e-j-allen-allan-pinkerton-left-chief-of-the-secret-service-of-the-united-states-at-secret-service-department-headquarters-army-of-the-potomac-near-antietam-maryland-october-3-1862-colorised-black-and-white-print-2H6B3FM.jpg)
President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department, Headquarters Army of
![Allan Pinkerton, chief of McClellan's secret service, with his men near Cumberland Landing, Virginia, 05-14-1862 522914 Stock Photo - Alamy Allan Pinkerton, chief of McClellan's secret service, with his men near Cumberland Landing, Virginia, 05-14-1862 522914 Stock Photo - Alamy](https://c8.alamy.com/zooms/6/20a9f85086204ccba083b548e103961a/dh2dkg.jpg)